The group also increased its full-year dividend by 5 percent to 8.86 pence per share.

"Our 2012 financial results reflect the significant exceptional costs associated with the Olympic contract and our overhead reduction programme, together with the large impairment charge related to the discontinued US Government Solutions business," CEO Nick Buckles said in the statement.

"Despite these issues, the underlying business has performed well in 2012 with an acceleration in organic turnover growth to 7 percent and with margins holding at over 7 percent. The acceleration in organic growth was due largely to a number of new North American commercial and UK government contracts and continued strong growth in developing markets and was achieved despite continued economic challenges in Europe."

G4S came under heavy criticism in the run-up to the London Olympics when it admitted to not being able to meet its contractual requirements to provide enough security staff for the two-week event. The controversy hived more than 17 percent from the group's share price over a four-day period and cost the company a key UK government contract to run one of the country's biggest prisons.

"The Olympic and Paralympic Games were a great success for the UK and we would like to reiterate our thanks to the military and the police for their support," said Buckles on 12 February. "We would also like to thank the 16,000 men and women of G4S who played their part in securing the Games despite the challenges faced by the group.

"We have accepted responsibility for the security workforce issues and, as a result of the settlement terms which we have announced today, have ensured that the overall cost to the taxpayer has been reduced significantly against the planned cost."

G4S shares fell 3.1 percent in the opening hours of London trading to change hands at 297.9 pence each. The shares have risen more than 25 percent since the worst of the market reaction to the Olympics issue in mid-July.